A rapid increase of a data volume of a mobile communications service places a strain on radio communications spectrums. In recent years, some spectrums are spared as radio television services and the like gradually exit from the market. However, the institute of electrical and electronics engineers (IEEE) does not allocate these spectrum resources to the 3rd generation partnership project (3GPP) for use. Therefore, for the 3GPP, such spectrum resources are unlicensed (unlicensed) spectrums, and are referred to as non-standard spectrums. Using an unlicensed spectrum for small cell deployment can offload data from a macro base station, thereby optimizing wireless network performance and improving user experience. If an unlicensed spectrum is used to transmit a multimedia broadcast multicast service (MBMS), the unlicensed spectrum may be effectively used, and more licensed (license) spectrums may be used for another service with a higher priority.
The unlicensed spectrum is a public spectrum but is not dedicated to the 3GPP, and any person or organization can use the spectrum to send information. Therefore, the unlicensed spectrum is not always available for the 3GPP. The 3GPP needs to contend with another system for permission to use the unlicensed spectrum. After the contention succeeds, the unlicensed spectrum can be used within a limited time but need to be released after use.
A cell using an unlicensed spectrum is referred to as a licensed-assisted access (LAA) cell. The unlicensed spectrum is not always available. Therefore, to use the LAA cell for communication, user equipment (UE) should first confirm whether the LAA cell is available. In a prior art, a base station (such as an eNB) first notifies the UE “which LAA cells may be available”. After receiving the notification, the UE monitors, at any time, whether these LAA cells are available. Once the UE discovers that an LAA cell is available, the LAA cell used immediately for data transmission. However, in the prior art, the UE needs to keep monitoring these LAA cells, and consequently, power consumption of the UE is quite large.
In a prior art, the base station first notifies the UE “which LAA cells may be available”. After receiving the notification, the UE keeps receiving signals of these LAA cells. When an LAA cell is available, the base station transmits data to the UE in a “cross-carrier scheduling” manner, that is, scheduling resources of the LAA cell by using a normal cell. Specifically, the base station sends, in the normal cell, downlink control information (DCI) to the UE. The DCI includes a modulation and coding scheme (MCS) of the data, an identity of the LAA cell having the data, a physical resource location of the data in the LAA cell, and the like. The UE demodulates, in the corresponding LAA cell, data according to the information. In the prior art, although the UE does not need to keep monitoring whether the LAA cell is available, the UE stills needs to keep receiving a signal of the LAA cell. Otherwise, when the normal cell notifies the UE that “the LAA cell has data”, the UE has no preparation, and it is too late for the UE to receive the data of the LAA cell.
Therefore, in the prior art, UE needs to keep monitoring or receiving a signal of an LAA cell, and consequently, power consumption is quite large.